Enable high-res CPU profile sampling for app startup

### Use case

Right now the CPU profiler in DevTools has to be manually started. You can ask it for any samples that may have been captured during startup, but they usually only cover a very brief window of time during startup.

### Proposal

There needs to be an option to start high-res CPU profiling sampling automatically, as soon as the app is started up, so that the startup activity can be fully profiled.